Adaptive immune response impairs the efficacy of autologous transplantation of engineered stem cells in dystrophic dogs

Duchenne muscular dystrophy (DMD) is the most common genetic muscular dystrophy, affecting 1 in 5000 male births. It is caused by mutations in the dystrophin gene, leading to absence of muscular dystrophin and a progressive degeneration of skeletal muscle and loss of function. Individuals with DMD exhibit progressive muscle weakness leading to the permanent use of a wheelchair in young adolescents, and to respiratory and heart failure in young adults. We have previously demonstrated that the exon skipping method safely and efficiently drives to the re-expression of a functional dystrophin in dystrophic CD133+ stem cells injected SCID/mdx mice. Golden Retriever dystrophic dogs (GRMD) represent the best pre-clinical model of DMD, mimicking the human pathology in many genotypic and phenotypic aspects, including the inter-individual heterogeneity. Here, we assess the capacity of serially and intra-arterially delivered autologous engineered dystrophic canine CD133+ stem cells of restoring dystrophin expression in GRMD. This is the first demonstration of five-year follow up study, showing initial clinical amelioration followed by stabilization in mild and severe affected GRMD dogs. However, the occurrence of T-cell response in three GRMD dogs, consistent with a memory response boosted by the exon skipped-dystrophin protein, suggests an adaptive immune response against dystrophin.